Sequenced crane boom

ABSTRACT

The invention concerns a hydraulically operated telescoping crane boom which is sequenced by means of a latch mechanism and sequencing valves such that the boom sections are automatically extended in order starting with the innermost section first. During retraction, the sequence is reversed; the outermost section being retracted first. Alternate forms are disclosed adding a manually operated section to the automatically operated boom and an entirely manually operated boom embodying the specific sequencing.

nite Stats atent n 1 @halupsky et al.

[ Nov. 6, 1973 SEQUENCED CRANE BOOM [75] Inventors: Paul A. Chalupsky;Oliver T.

Nephew, both of Cedar Rapids, Iowa [73] Assignee: FMC Corporation, SanJose, Calif.

[22] Filed: Apr. 15, 1971 [21] Appl. No.: 134,243

Related U.S. Application Data [62] Division of Ser. No. 780,993, Dec. 4,1968,

abandoned.

[52] U.S. Cl 212/55, 52/115, 91/169 [51] int. Cl. B66c 23/06 [58] Fieldof Search 212/54, 55, 144;

[56] References Cited UNITED STATES PATENTS 3,462,023 8/1969 Grove212/55 FOREIGN PATENTS OR APPLlCATlONS 1,268,804 5/1968 Germany 212/55476,625 9/1969 Switzerland ..212/55 Primary ExaminerHarvey C. HornsbyAtt0rney-F. W. Anderson et al.

[57] ABSTRACT The invention concerns a hydraulically operatedtelescoping crane boom which is sequenced by means of a latch mechanismand sequencing valves such that the boom sections are automaticallyextended in order starting with the innermost section first. Duringretraction, the sequence is reversed; the outermost section beingretracted first. Alternate forms are disclosed adding a manuallyoperated section to the automatically operated boom and an entirelymanually operated boom embodying the specific sequencing.

14 Claims, 26 Drawing Figures PATENTEI] NOV 6 I973 SHEET 10F 9INVENTORS. PAUL A. GHALUPSKY OLIVER T. NEPHEW ATTORNEYS PATENIEUNUY6197s 8.770.138

SHEET ucr 9 INVENTORS PAUL A. CHALUPSKY OLIVER T. NEPHEW aa/4m ATTORNEYSPATENTEDNUV 8|973 4 3370.138

SHEET SUF 9 F'IB IE PAUL A. CHALUPSKY OLIVER T. NEPHEW 8 a 7-: ATTORNEYSPATENTEDHUV s 1975 swans SHEET 7 BF 9 I I 20in. 5Q 4 56 INVENTORS PAULh. GHALUPSKY OLIVER T. NEPHEW ATTORNE Y5 SEQUENCED CRANE BOOM This is adivision of application Ser. No. 780,993 filed Dec. 4, 1968, nowabandoned.

BACKGROUND OF THE INVENTION The present invention relates to manual andautomatically operated hydraulic telescoping crane booms such asemployed on mobile transporters, and Wreckers or in fixed installations.

DESCRIPTION OF THE PRIOR ART One of the most important objectives incrane boom design is to reduce the weight of the extended boom to aminimum while retaining the required structural rigidity and strength inthe boom for lifting. All components of the boom which are notstructural increase the bending moment loads on the boom and transporteror mounting; and thereby decrease the lifting capacity of the crane inproportion to their weight and distance outward from the boom pivot ormount.

In presently employed cranes of the type having telescoping booms, thesequence in which the telescoping sections of the boom extend isgenerally determined by the relative friction between each oftelescoping sections.

In practice, the innermost section usually extends first for a shortdistance until its overhang causes an increase in friction. The nextinnermost section then starts to extend. The extension of thetelescoping sections therefore is progressive or entirely random innature.

This characteristic is undesirable in that unnecessary structural andnonstructural weight is moved outwardly, substantially reducing thelifting capacity of the crane, except in the case where the boom is usedin its fully extended position.

Another undesirable characteristic of presently employed telescopingbooms is that the hydraulic cylinders which extend and retract the boomare base-end driven, requiring flexible hoses and reel mechanisms toprevent hose entanglement. The high pressure flexible hoses are heavierthan tubing and the additional weight of the reel mechanisms furtherreduces the load lifting capacity of the crane.

SUMMARY OF THE INVENTION An object of the present invention is toprovide a telescoping crane boom with an increased lifting capacity byreducing the non-structural extended weight of the boom. This object isachieved by an arrangement employing rod-end driven hydraulic cylinders,eliminating the requirement for flexible lines and reel mechanisms toprevent their entanglement.

Another object is to reduce the non-structural extended weight byeliminating the progressive or random extension of the telescopingsections by employing a predetermined sequence of extension andretraction.

A further object is to automatically control the extension sequence by asequencing latch mechanism which releases the sections for extension insuch a manner that the telescoping sections are permitted to extendconsecutively beginning with the radially innermost unextended section.

Another object is to automatically control the retraction sequence by ahydraulic sequencing valve in cooperation with the rod-end drivencylinders which have pilot operated check valves. The telescopingsections are retracted consecutively beginning with the radiallyoutermost extended section. If the sequencing valves are not employed,the latching mechanism can be employed to control the retractionsequence.

Additional objects of sequencing valve are to act as bypass valve duringthe extension sequence and act as a safety valve, preventing collapse ofthe boom if a line interconnecting the hydraulic cylinders should fail.

Alternate forms of the invention are shown wherein boom sections can behydraulically extended only by manually pinning and repinning boomsections to achieve sequenced extension and wherein the manual andautomatic extension mechanisms are combined.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective of thesequenced crane boom of the present invention mounted on a transporter.

FIG. 2 is an enlarged fragmentary diagrammatic longitudinalcross-section of the boom of FIG. 1.

FIG. 2A is an enlarged view of a portion of FIG. 2 showing the latch ina different operating position.

FIG. 3 is an enlarged section of the boom taken on line 3-3 of FIG. 2.

FIG. 4 is a cross-section of a hydraulic cylinder that is mounted insidethe boom, along the lower wall thereof.

FIG. 5 is an enlarged section of the rod end of the cylinder, showingthe pilot valve, taken on line 55 of FIG. 4.

FIG. 6 is an enlarged section of the pilot valve, the view being takenon line 6-6 of FIG. 4.

FIG. 7 is an enlarged sectional view of the left end of FIG. 4 showingthe sequencing valve of the hydraulic cylinder in the closed position.

FIG. 8 is a vertical section, similar to the left end of FIG. 2, butshowing another embodiment of the crane wherein the head machine isconnected directly to the boom section.

FIGS. 9 and 10 are schematic showings of the sequential extension of theboom sections in accordance with the present invention.

FIG. 11 is a schematic of the hydraulic system with both cylinders ofthe system in the retracted position.

FIG. 12 is a schematic, similar to FIG. 11, with the upper cylinderfully extended and the lower cylinder partially retracted.

FIG. 13 is a schematic, similar to FIG. 11, with the upper cylinderpartially retracted and the lower cylinder fully retracted.

FIG. 14 is a fragmentary vertical section, similar to FIG. 7, butshowing a modified embodiment of the hydraulic cylinder wherein thesequencing valve has been removed.

FIG. 15 is an enlarged view of a modified pawl and inner boom section.

FIGS. 16-19 are schematic views showing the sequential extensions of theboom sections in accordance with the modified hydraulic cylinder of FIG.14.

FIG. 20 is an enlarged fragmentary longitudinal cross-section of analternate form of the boom.

FIGS. 21-24 are schematic showings of the sequential extensions of theboom sections of the alternate form shown in FIG. 20.

FIG. 25 is a fragmentary longitudinal section, similar to FIG. 7,showing a further embodiment of the present invention.

DESCRIPTION OF A PREFERRED EMBODIMENT As seen in FIG. 1, hydraulicallyoperated telescoping boom is shown mounted on a mobile transporter 22.The transporter 22 is driven by an engine 24 that also provides power tothe hydraulic system which operates the boom 20. Located adjacent to thenormal controls associated with the transporter are controls 26 for thehydraulic system such as manually actuated levers. Adjustable outriggers28 are located at the four corners of the transporter to provide awider, more stable base for the crane when lifting large loads.

The boom 20 is mounted in a support 30 which includes a counterweight32. The support 30 is rotatably mounted on a ring and traversingmechanism 34 which in turn is mounted on the frame 36 of thetransporter. A hydraulic swivel 38 is employed to transmit hydraulicfluid from the stationary to the rotating portion of the crane. A pairof hydraulic elevating cylinders 40 (one only being shown) mountedbetween the support and a plate 41 secured to the boom are employed tolift the boom 20 to the desired elevation.

A cable 42 extends from an hydraulic winch 44 mounted in the support 30to a head machine 46 on the end of the telescoping boom 20.

TELESCOPING BOOM The telescoping boom 20, seen in FIGS. 1 and 2 iscomprised of sections 48, and S2. The outer section 48 which is notextendable, is pivotally mounted on pin 54 for rotation in a verticalplane by the elevating cylinders 40. The intermediate telescopingsection 50 is mounted within the outer section 48. A sequencing latchmechanism 56, to be described later, interconnects the outer section 48and intermediate section 50. Located within the intermediate section 50is the inner telescoping section 52 on which the head machine 46 ismounted.

The internal arrangement of the telescoping boom sections is shown inFIG. 2. An upper hydraulic rodend driven cylinder 58 is attached to theintermediate boom section 50 at its rod end 60 by a pin 62. Forcetransmitting lugs 64 (FIG. 3) on both sides of the cylinder 58 haveinner opposing straight vertical faces 65 (FIG. 2) that exert theextension and retractionforces of the cylinder against a pair ofvertical pins 66 that are mounted between bosses 68 of the inner boomsection 52. Sufficient clearance is provided between the lugs 64 andpins 66 to permit tilting of the pins 66 in the vertical plane due todeflection of the boom under load without producing and induced bendingmovement in the cylinder. Therefore, as the hydraulic cylinder 58extends, the inner boom section 52 is extended with respect to theintermediate boom section. As a result of the rearward lug position, theeffective length of the cylinder subject to buckling and bendingstresses is reduced by one-half permitting a lighter weight cylinderdesign.

The intermediate boom section 50 is extended by means of a similar,lower rod-end driven hydraulic cylinder 70. The cylinder 70 is attachedto the fixed outer boom section at its rod end 72 by the boom mountingpin 54 which also attaches the boom to the support 30. Lugs 74 havinginner opposing faces 75 on each side of the cylinder 70 transmit theforces developed by the cylinder to a pair of vertical pins 76. The pins76 are mounted between bosses 78 of the intermediate boom section 50 inthe manner described in connection with the pins 66 and bosses 68.

Lower wear strips 80 and 82 are located on the lower rear portions ofthe inner and intermediate boom sections, respectively, to reduce thesliding friction of the telescoping sections. Upper wear strips 84 and85 are pivotally mounted on pins 86 and 87 respectively at the upperrear portions of the telescoping sections. Similar wear strips 88 and89, pivoted on pins 90 and 91, respectively, are located at the lowerforward end of sections 48 and 50. The pivoting action of the wearstrips 84,85, 88 and 89 prevents binding of the boom sections when theyare under load.

SEQUENCING LATCH MECHANISM The purpose of the sequencing latch 56 is tocontrol the order in which the telescoping boom sections extend andretract. The latch mechanism, FIGS. 2 and 2A is comprised of a dog 92that is attached to a steel finger 94 which is mounted on the outer boomsection 48. The dog engages a notch 96 in the upper surface of a pawl 98which has an upwardly projecting abutment 98a. The pawl is rotatablymounted between a pair of lugs 100 of the intermediate boom section 50.A roller 102 on the lower surface of the pawl 98 maintains the pawl inthe raised position (FIG. 2) such that it engages the dog 92 as long asroller 102 is supported by the upper surface of the inner boom section.When the pawl 98 is in the raised position, the intermediate 50 andouter boom sections 48 are locked together by the pawl 98 and dog 92.Also, it will be noted that when these boom sections are lockedtogether, the lower bydraulic cylinder 70 is held in the retractedposition.

As will be explained more fully presently, during boom extension theinner boom 52 moves relative to the latched outer boom 50 and, as theinner boom section reaches its maximum extension, the roller 102 of thelatch mechanism drops into a hole 104 in the top of the inner boomsection 52. As the pawl drops into its lowered position, the dog 92 isdisengaged from the notch 96 thereby unlocking the intermediate andouter boom sections as shown in FIG. 2A and permitting the intermediateboom to move away from the fixed outer boom 48. v

The sequence is performed in reverse upon retraction such that theintermediate boom section 50 is retracted first and the inner section 52thereafter.

HYDRAULIC SYSTEM A hydraulic sysem 108 (FIG. 11) is employed to extendand retract the telescoping boom section. The system comprises a pump110, a reservoir 1 12, a reversing valve 114 and the upper and lowerboom actuating hydraulic cylinders 58 and 70, respectively. From thepump 110, reservoir 112 and controls 26, two hydraulic lines 116 and 118lead to the hydraulic swivel 38 in the support 30. The hydraulic swivel38 is of a common type having an inner fixed member containing multiplepassages connected to the inlet lines. The multiple passages communicatewith annular grooves in the outer rotating member. Each groove in turnhas an outlet port to which the outlet hydraulic lines are attached.From the swivel 3 the lines 116 and 1 18 are routed and attached to anadapter block 120 (FIG. 2) mounted on the outer boom section. From theadapter block L20, the line 116 leads to a fitting 121 formed on the rodend of cylinder 58, and the line 118 leads to a fitting 123 that isformed on the rod end of the cylinder and provides a rod-retract port124.

The hydraulic cylinders 70 and 58 are identical, and only the lowercylinder 70 will be described in detail. Each cylinder includes a fixedinner cylinder 117 and an outer cylinder 119 that telescopes over theinner cylinder 117. The inner cylinder includes a rod end wall 117a,spaced cylindrical members 117b and 117C, and a second end wall 117d allwelded together to form a rigid unit. A plurality of annular spacers117e, l17f, and 117g are secured on the unit by a locking ring l17h. Theouter cylinder 119 includes an outer sleeve 1 19a that telescopes overthe inner cylinder and is held in spaced relation to the cylinder by anut 119b. An end member 1196 is welded to sleeve 119a and receives a nut119d which locks a valve assembly 125 in the end of the cylinder to forman end wall. The valve assembly comprises a body member 125a, and anannular spacer 125b, that has large passages through its periphery andbears against a valve seat 1250. A two-piece valve stem 125d is slidablydisposed in the body 125a and is urged away from the end of the cylinderby a spring 125e. Suitable seal rings are disposed between the movablesurfaces of the cylinder.

The hydraulic conduit 116 communicates with a port 122 in an upperextension of the rod end wall 117a of the cylinder. Fluid flows fromport 122 downwardly through a passage 126 to a chamber 127 of a pilotcheck valve 128. The fluid flows around a stem 130 of the valve, unseatsa spring-loaded ball 132 when fluid pressure is about I00 psi, andpasses through a passage 136 into the central chamber of the cylinder.At the far end of the chamber the fluid passes through an opening 138 inwall 117d and enters a chamber that will be referred to as the extend"cavity.

If the valve stem 125d of valve 125 is in the open position shown inFIG. 4, the fluid in the extend cavity can flow around the stem 125d,through the large passages formed in the annuar spacer l25b and into apassage 148 in the member 1196. A fitting 150 receives a conduit 151which extends along the cylinder to a connector 152 (FIG. 2) that ismounted on the cylinder. A conduit 154is secured between the connector152 of the lower cylinder 70 and the port 122 of the upper cylinder 58.

As mentioned the upper cylinder 58 is identical to the lower cylinder,however, the connector 152 on the casing of the upper cylinder is closedby a plug 156.

Referring to FIG. 4, it will be seen that the line 118 communicatesthrough port 124 with a passage 158 that extends into an annular passage160 from which ports 162 communicate wtih a retract chamber 164. A pilotchannel 166 (FIG. 6) connects the annular passage 160 with the pilotvalve 128. An exhaust port 168 (FIG. 4) connects the retract chamber 164with a connector 171 that receives a conduit 172. The connector 171 isformed on the cylinder alongside the connector 152 and, in FIG. 2, theconnector 171 is hidden by connector I52 and the conduit 172 is hiddenby conduit 154. However, it will be understood that the conduit 172extends from connector 171 to the rod retract port 124 in the fitting123 of the upper cylinder 58.

In the embodiment of the crane illustrated in FIG. 2, the head machineis connected to boom section 52 by an auxiliary boom section in the formof a rectangular tube 182 that is welded to the head machine, isdisposed inside boom section 52, and is connected thereto by a removableboom-locking pin 187 that extends transversely throughaligned openings187a in the section 52 and in the tube 182. For a purpose that will beexplained presently, a removable pin 184 is disposed in aligned openings185 in an extension bar 186 of the case end of the cylinder 58 and inthe tube 182. When the pin 184 is not in place, the case end of thehydraulic cylinder is supported by a roller 186 mounted on extension bar186.

In another embodiment, the head machine is connected directly to theinner boom section 52, as by welding, as shown in FIG. 8 and thesequenced extension and retraction of the boom sections will beexplained in connection with the FIG. 8 embodiment. It will of course beunderstood that both embodiments are identical except for the manner ofconnecting the head machine to the inner boom section.

OPERATION The operation of the crane in elevating, rotating and hoistingis accomplished in a manner well known in the art. The extension andretraction of the telescoping boom sections is the subject of thepresent disclosure and will now be described with reference to FIGS.8-12.

To effect extension of the boom 20, a control is actuated to dispose thereversing valve 114 in the position shown in FIG. 11, supplying pressureto line 116 from the pump 110. The hydraulic fluid flows into thechamber 134 of the lower hydraulic cylinder through the pilot valve 128.The fluid then flows through the passage 138 into the extend cavity 140of the cylinder 70.

At this time, the latch 56 (FIG. 8)has locked the intermediate boomsection 50 to the non-extendable outer boom section 48 and theintermediate boom section 50, acting through the pins 76 (FIG. 9) andhas locked the lower cylinder 70 in retracted position. The sequencingvalve (FIG. 11) of the lower cylinder 70 is held in the open positionwhenever the cylinder is in the fully retracted position due to theengagement of the stem 125d with the wall member 117d, and allows thefluid to flow to the upper cylinder 58 through line 154. The path offluid flow in the upper cylinder 58 is identical to that of the lowercylinder 70; however, the extend cavity of the upper cylinder is closedby the plug 156, and therefore the upper cylinder 58 extends, extendingthe inner telescoping section 52 of the boom 20 through the engagementof the lugs 64 on the cylinder casing with the pins 66 as shownschematically in FIG. 9.

The lower cylinder 70 is prevented, from extending until the innertelescoping section has been fully extended and has actuated the latchmechanism to release the lower hydraulic cylinder 70. When cylinder 70is released, it is extended and it extends the intermediate boom section50 through the engagement of the lugs 74 with the pins 76 as seen inFIG. 9. After the lower cylinder 70 has extended approximately one-halfinch, the sequencing valve 125 is closed by spring 125e preventing thecollapse of the cylinder 70 if the line 154 between the upper and lowercylinders should fail. No flexible liries are required between thecylinders since there is no motion between the case end of the lowercylinder and the rod end of the upper cylinder.

During retraction, it is desired that the intermediate boom section 50retracts before the inner section 52. When the reversing valve 114 ismoved to the position shown in FIG. 12, fluid under pressure enters line118, passes through the hydraulic swivel 38 and enters the annularpassage 160. The fluid then enters the retract cavity 164 of the lowercylinder 70. The retract cavity of the upper cylinder 58 is similarlypressurized by fluid from line 172 which exits from the lower retractcavity 164 through port 168. Simultaneously, both pilot channels 166 arepressurized and the pilot valves 128 of both cylinders are opened whenthe retract pressure has reached approximately 100 psi. Upon opening ofthe pilot valves 128, the fluid in both extend chambers would ordinarilybe allowed to escape from the cylindei's; however, the fluid of theupper cylinder 58 which is exhausted through line 154 is blocked by theclosed sequencing valve 125 of the lower cylinder 70 as seen in FIG. 12.The blocking action of the sequencing valve prevents retraction of theupper cylinder 58 and the inner boom section 52 which is controlledthereby until the lower hydraulic cylinder 70 has completely retractedthe intermediate boom section 50 (FIG. 13).

The retraction of the lower cylinder 70 opens the sequencing valve 125,unblocking the conduit 154 and allowing the upper cylinder 58 to retractin response to pressure in the retract chamber 164. As the intermediateboom section approaches its retracted position, the abutment 98a of thepawl engages the dog 92, causing the pawl to rotate counterclockwiseinto locked engagement with the dog.

The embodiment shown in FIG. 2 which features a particular manner ofconnecting the head machine 46 to the inner boom 52 is used when anadditional boom length is desired. In general this is accomplished bydisconnecting the auxiliary boom section 182 from the inner boom section52; looking all three boom sections 52,50 and 48 together so they cannotbe extended; disconnecting the upper power cylinder 58 from the innerboom section and connecting it to the auxiliary boom section 182;energizing the cylinder to hydraulically jack the auxiliary section toan extend position; reconnecting the auxiliary section to the inner boomsection; disconnecting the cylinder from the auxiliary boom section andreconnecting it to the inner boom section; and unlocking the boomsections 48, 50 and 52 from each other. When the boom sections aresequentially actuated as previously explained, the boom will have theadded reach provided by the extended auxiliary boom section 182.

The locking of the boom sections 48,50 and 52 to each other isaccomplished by raising the two pins 66 upwardly through holes 190 inthe plate 41 secured to the outer boom section until transverse threadedholes 188 in the pins 66 are disposed above the plate. Capscrews (notshown) are then threaded into the holes 188 to lock the pins in thiselevated position in which their lower end portions are out ofengagement with the lugs 64 of the upper cylinder. Since the pins 66 areengaged in aligned holes in the three boom sections 48, 50 and 52, theyare locked against forward movement.

The pin 187, which is securing the inner section 52 to the auxiliaryboom section, is then withdrawn from the aligned holes in the booms topermit movement of the auxiliary section.

The cylinder 70 is then energized by directing pressurized fluid throughconduit 116 into the hydraulic system.

When the auxiliary boom section is extended to a position where anaperture 187!) near its trailing end portion is aligned with the twoapertures 187a in the inner boom section 52, the power cylinder isde-energized and the pin 187 is inserted through the two apertures 187aand the aperture 187b to connect the auxiliary boom section 182 in itsextended position to the inner boom section.

The pin 184 is withdrawn from the forward extension of the powercylinder and the power cylinder is retra cted to a position wherein thepins 66 can be lowered to a position between the lugs 64.

The sequential actuation of the boom sections as explained in connectionwith the FIG. 8 embodiment is then carried out.

In a further embodiment of the invention, the structure is substantiallyidentical to the structure of either of the embodiments illustrated inFIG. 2 or FIG. 8, and in the illustrations of FIGS. 14-19, parts thatcorrespond to identical parts of FIGS. 2 or 8 will be given the samereference numerals followed by a prime mark. The embodiment of FIGS.14-19 differs in three areas: (I) the pawl of the latch mechanism isprovided with a hooked end 200 as shown on the pawl 201 of FIG. 15, (2)the valve assembly at the case end of each power cylinder has no valvestem, as shown by the valve assembly 203 of FIG. 14 in the powercylinder and (3) a bar 205 (FIG. 15) is welded on the upper surface ofthe inner boom section. With this arrangement the advantageoussequencing of the boom sections can be accomplished without using asequencing valve since the engagment of the hooked end 200 of the latchpawl with the bar 205, will, in a manner to be described presently,prevent retracting movement of the inner boom section 52' until theintermediate section 50' has been retracted.

Referring to FIG. 16 the unextended position of the boom sections 48,50' and 52' is illustrated. When the control lever is actuated to directpressurized fluid into the hydraulic system through the ports adapted tocause extension of the upper cylinder 58' and the lower cylinder 70, theupper cylinder 58' will be extended while the lower cylinder will notextend due to its locked connection with boom section48' through pins 76and latch mechanism 56'. When the inner boom reaches its extendedposition, the roller 202 of the latch mechanism drops into the hole 104in the boom section 52', permitting the pawl 201 to drop downwardly outof latched engagement with the dog 92f. The intermediate boom section 50is now free to be extended. As the section 50 starts to move, the hookedend 200 of the pawl drops behind the bar 205 on the boom section 52'.The boom sections 52 and 50 then move outwardly together. When the lowercylinder 70' has been fully extended, the boom is in fully extendedposition.

When the boom is to be retracted, the control lever is actuated todirect pressurized fluid to the cylinders 58 and 70' in a direction tocause retraction of the boom sections. Since the valves 203 in the caseends of cylinders 58' and 70' do not have valve seating members, thepressurized fluid that has caused extension of the boom sections can bevforced back to the sump when pressurized fluid is applied to theopposite ends of the cylinders. Accordingly, when pressure is applied tothe case ends of the cylinders, they both try to retract. However, thehooked engagement of pawl end 200 and the bar 205 on the inner sectionas shown in FIG. 18 prevents the inner boom section 52' from retractingrelative to the boom section 50'. Since the cylinder 58' cannot retract,the cylinder 70 does retract and thereby retracts the intermediate boomsection 50.

As the latch mechanism 56' reaches the fixed dog 92', the upper end 261aof the pawl 201 engages the dog, causing the pawl to pivotcounterclockwise (FIG. and move away from the bar 205. The inner boomsection is thus freed, and the power cylinder 58' retracts and moves theinner boom section to retracted position.

Another embodiment of the present invention is illustrated in FIG. 20.In this arrangement the boom sections are similar to those in FIG. 2and, in describing this embodiment, parts that correspond to identicalparts of HG. 2 will be given identical reference numerals followed by adouble prime .mark.

In general the mechanism includes a fixed outer boom section 48", anintermediate boom section 50", an inner boom section 52", and anauxiliary boom section 182". A power cylinder 70 that is identical tocylinder 70 with the exception that connection 152" is capped by a plug210 rather than being in communication with a second cylinder.

A pin 76" is adapted to establish a driving connection with lugs 74" ofthe cylinder 70" and is further provided with a threaded transverse hole212 which is adapted to receive a threaded pin 214 when the pin 76" israised to the full line position of FIG. 20. When the pin 214 isinserted in the hole 212, the pin 76" is held in elevated position, outof engagement with the cylinder 70" but locking the outer boom section48 to the intermediate boom section 50".

A pin 216 is removably positioned in aligned holes in the boom sections48", 50", and in the upper boss 68" of the inner boom section 52" tolock all three boom sections against relative longitudinal movement.

The cylinder 70 is provided with an extension 218 that is supported by aroller 220. The extension 218 is provided with an inclined arm 222 thatis welded to extension 218 and is provided with two spaced holes 222aand 222b.

The auxiliary boom section 182 has a pair of aligned holes 224 (one onlybeing shown) near its forward end, a pair of aligned holes 226 (one onlybeing shown) spaced rearwardly of the holes 224, and a pair of alignedholes 228 near the rear end of the section. The inner boom section 52"has a pair of transversely aligned recesses 230 on its forward edge, twopairs of aligned holes 231 and 232 rearwardly of the forward edge, and apair of aligned holes 234 near its rearward end (one hole of each pairbeing shown). The intermediate boom section 50" has a pair of alignedholes 235 (one only being shown) near its forward end. A pin 236 isnormally positioned in the six aligned holes 226, 232 and 235 to lockthe sections together.

The boom is extended in the following manner. With the elements in theposition shown in FIG. 20, the pin 236 is first removed, and a pin 238is positioned in the hole 222a of the cylinder extension 222 and in thetwo aligned holes 224 of the auxiliary boom section 182" as shown inFIG. 21. Pressurized fluid is then directed into the power cylinder 70"in a direction to cause the cylinder to extend and move the auxiliaryboom section to the position of FIG. 21 wherein holes 228 in boomsection 182" are aligned with holes 231 in boom section 52". The pin 238is removed, and the cylinder 70" retracted until the hole 222b becomesaligned with the four aligned holes 228 and 231. A pin 240 is placed inthe five aligned holes as seen in FIG. 22 and vertical pin 216 isremoved from its locking engagement with the boom sections. Then, whenthe cylinder is extended, the inner boom section 52" and the auxiliaryboom section 182 are moved to the position of FIG. 23, bringing thealigned holes 234 of section 52" into alignement with the holes 235 inboom section 48". The pin 240 is removed, the power cylinder '70" isretracted, and the pin 240 is replaced in the four aligned holes 228 and231 to lock sections 182" and 52" together during subsequent extensionsof the other sections.

The vertical pins 76" are now lowered to a position between the lugs 74"of the cylinder 70" and, in this lowered position, they are free of theouter boom section 48". A pin 244 is placed in the four aligned holes234 and 235. The power cylinder 70 is again extended and, through thepin 76, it drives the intermediate boom section 50" outwardly. Section50", in turn, drives the inner section 52" outwardly through the pin244. The boom is now in fully extended position.

To retract the boom, the sequence is reversed. The power cylinder 70" isretracted, to pull the intermediate section 50" inward. The pin 244 isremoved and the vertical pins 76" are raised to the full line positionof FIG. 20. The pin 240 is removed from the four aligned holes 228 and231, the cylinder 70 is extended and the hole 222b of the cylinder isbrought into alignment with these four holes, and the pin is placed inthe five aligned holes. The cylinder is retracted, to draw the innercylinder 52" inwardly. The pin 240 is once more removed, the cylinder isextended to bring the hole 222a into alignment with the two alignedholes 224 of the auxiliary boom section 182", the pin 238 is inserted inthe three aligned holes, and the cylinder is retracted to move theauxiliary section back to the position of FIG. 21.

Another embodiment of the invention incorporates a dual actionsequencing valve assembly 250 seen in FIG. 25, which is a modificationof the sequencing valve employed in the hydraulic cylinder 70 of theoriginal embodiment shown in FIG. 7. The modifications incorporated inthe valve 250 perform the functions of both the valve 125 and latchmechanism 56.

The valve assembly 250 mounted in the end of a hydraulic cylinder 70"comprises a body member 125a" and an annular spacer l25b" that has alarge passage through its periphery and bears against a valve seat 252.The valve seat 252 has an extension 254, of a smaller diameter than thebody of the seat at 256 which I extends into a cavity 258 formed in anend wall 117d" of a cylinder rod 117".

In order to isolate the cavity 258 from the extend cavity a seal ring260 is installed in an annular groove 262 in extension 254. A two piecevalve stem 125d" is slidably disposed in the body 125a" and is urgedtoward the valve seat 252 by a spring l25e". In addition, seal rings arelocated between the movable and stationary surfaces of the valve andcylinder.

A check valve 264, which releases at approximately 2,000 psi, is locatedin the end member 266 of the cylinder and is effective to permit flowbetween the port in spacer 12512" and the extend cavity 140 throughpassage 268 and clearance space at 269 between the end of member 117 andmember 266.

To prevent a hydrostatic lock from forming in cavity 140" as the outercylinder 119 is retracted, a low pressure relief valve 270 is disposedin the valve seat 252 such that any fluid captured in the extend cavity140" during retraction is allowed to escape.

Hydraulic fluid is supplied to the dual action sequencing valve throughan opening 138" in the end wall 117d and exists through a passage 148 inthe outer cylinder member 266. Thereafter the fluid enters a conduit151" through a fitting 150" in a similar manner as in the initialembodiment, since the remainder of the hydraulic cylinder 70 as well ascylinder 58 and the boom sections are unchanged except for the removalof the latch mechanism 56.

in the present embodiment the dual action sequencing valve 250 isemployed only in the lower hydraulic cylinder 70". To describe theoperational sequence of the dual action valve 250 it is assumed thatinitially the boom 20 is fully retracted.

To effect extension of the boom 20 a control is actuated such thathydraulic fluid is supplied to the lower hydraulic cylinder 70". Thefluid enters the valve 250 through passage 138" and flows through thepassages, as indicated by the arrows in FIG. 25, exiting through theconduit 15!". The fluid is then conducted through the upper cylinder 58and into the extend cavity 140.

As the pressure in both the hydraulic cylinders 58 and 70" starts torise, both cylinders exert an extending force. in this case both theinner and intermediate boom sections are free to extend, there being nolatch to restrain them. However, the inner boom section 52, which isconnected to cylinder 58, extends first because the upper cylinder 58generates a substantially greater extending force than the lowercylinder 70". This fact can be readily determined by comparing theeffective areas of the extend cavity 140 of the upper cylinder 58 (FIG.4) which is identical in end area to cavity 140 of FIG. 25 and cavity258 which is considerably smaller. Although the difference in frictionbetween the inner and intermediate boom sections which resists theirextension varies, the substantial difference in the effective area ofcavities 140 and 258 insures that the upper cylinder 58 and attachedinner boom section 52 will extend first.

Upon complete extension of the upper cylinder 58 the pressure in thehydraulic system rises. An aproximately 2000psi the check valve 264opens and the extend cavity 140" of the lower hydraulic cylinder 70" ischarged with hydraulic fluid causing the lower cylinder and the attachedintermediate boom section to extend. As soon as the lower cylinder 70"has extended a sufficient distance such that the extension 254 hasdisengaged cavity 258, the action of spring 1251:" closes valve stem125d" against seat 252 preventing the collapse of cylinder 70" in theevent of damage to the upper cylinder 58 or interconnecting lines.

To retract the boom from the fully or partially extended position,hydraulic pressure is applied to the retract cavities of both cylindersas described in the initial embodiment. As the upper cylinder attemptsto retract and force the fluid out of its extend cavity back throughconduit 151" into cylinder 70, the valve stem 125 which is now seated inthe vaive seat 252, blocks the extend fluid" from the upper cylinder,preventing the retraction of the upper cylinder 58 and attached innerboom section 52. The lower hydraulic cylinder 70" and attachedintermediate boom section 50 which is not similarly restrained; retract.As the lower cylinder 70 approaches the end of its retract stroke, thevalve seat extension 254 engages and seals in cavity 258. The reliefvalve 270 is now effective to allow the fluid which becomes trapped incavity 140" to escape, permitting full retraction of the lower cylinderDuring this portion of the retract stroke the valve stem d" contacts theend wall 117d", unseating the valve against the force of spring l25e"and thereby releasing the extend fluid of the upper hydraulic cylinder58. The upper cylinder 58 and attached inner boom section 52 now retractin response to the retract pressure in the upper cylinder, completingthe retraction of the entire boom assembly 20.

Although the best mode contemplated for carrying out the presentinvention has been herein shown and described, the subject matter whichis regarded as the invention is set forth in the appended claims.

We claim:

1. In a telescoping boom having an outer fixed section and intermediateand inner sections that are extended and retracted by hydrauliccylinders, each of said hydraulic cylinders being connected at one endto the boom section to be extended and at the other end to the nextradially outermost boom section, each cylinder including two sets ofdiametrically opposed lugs disposed to receive a pin between them, andmeans on said booms defining bosses for retaining pins received betweenthe said lugs, said lugs cooperating with said pins and bosses totransmit the cylinder forces to the boom sections for extension andretraction.

2. In an extensible boom of the type having a tubular base section, atubular mid section slidably received in said base section, a tubularinner section slidably received in said mid section, first hydrauliccylinder means pivotally connected to base section and disposed in saidbase and mid sections, second hydraulic cylinder means pivotallyconnected at one end to said mid section and disposed in said-mid andinner sections, the improvement which comprises laterally spaced lugmeans radially disposed on opposite sides of each of said cylinders,means defining alignable openings in said base and in said mid and innerboom sections, first pin means insertable through the apertures in saidmid section when in alignment and between said lug means of said firstcylinder connecting said first cylinder in driving engagement with saidmid section, and second pin means insertable through the apertures insaid inner section and between said lug means of said second cylinder toconnect said second cylinder in driving relation with said innersection.

3. The apparatus of claim 6 including an auxiliary section slidablyreceived in said inner section and disposed in a surroundingrelationship to said second cylinder connector means secured to theoutward end of said cylinder, third removable pin means insertablethrough alignable openings in said connector means and said auxiliarysection; and retaining means for retaining said second pin means in apartially inserted position in the aligned apertures of said base, midand inner sections but out of engagement with said lugs whereby saidbase, mid and inner sections are locked together and said lugs on saidsecond cylinder are disengaged whereby energization of said secondcylinder causes extension of said auxiliary section.

4. The apparatus of claim 2 wherein said lateral spacing between saidlugs is defined by straight vertical surfaces and said pin meansvertically receivable therein have a diameter less than said spacing topermit relative sliding and tilting motion between said lugs and saidpin means upon deflection of the boom under load.

5. The apparatus of claim 2 wherein each cylinder includes a casing anda rod and wherein said lugs are located at the rear portion of eachcasing.

6. In a telescoping boom having concentric sections including an outerfixed section and intermediate and inner sections that are extended andretracted by hydraulic cylinders, each of said hydraulic cylinder beingconnected at one end by pin means to the boom section to be extended andat the other end to the next radially outermost boom section, whereinthe improvement comprises an extendible auxiliary boom section within.

said inner section, pin and aperture means effective to alternately locksaid inner and auxiliary sections together when said auxiliary sectionis either in a fully extended position or in a fully retracted position,said pin and aperture means also being effective to connect thehydraulic cylinder associated with said inner section to the auxiliarysection for extension and retraction thereof, and the pin meansassociated with said inner section being movable to a position where theassociated hydraulic cylinder is disconnected therefrom and said inner,intermediate and outer sections are locked together.

7. A method of extending a crane boom, having at least two extendibletelescopigng sections mounted within a fixed section by means of asingle hydraulic cylinder having its driving end attached to said fixedsection, comprising the steps of connecting the driven end of saidcylinder to the first section to be extended, connecting the remainingsections to said fixed section, extending said first section byextending said hydraulic cylinder, locking said first section to asecond section, disconnecting said driven end of said cylinder,retracting said cylinder, connecting the driven end of said cylinder tosaid second section, disconnecting said second section from said fixedsection, and extending said second section by extending said hydrauliccylinder.

8. A method of extending a telescoping boom having concentric sectionsincluding an outer fixed section, intermediate, inner and auxiliarysections wherein a first hydraulic cylinder has its driving endconnected to said fixed section and its driven end to said intermediatesection, a second hydraulic cylinder has its driving end connected tosaid intermediate section and its driven end to said inner sectioncomprising the steps of connecting the driven end of said secondcylinder to the auxiliary section to be extended, disconnecting thedriven end of said second cylinder from said inner section, locking theremaining sections to said fixed section, extending said auxiliarysection by extending said second hydraulic cylinder, locking saidauxiliary section to the inner section, disconnecting said driven end ofsaid second hydraulic cylinder, retracting said second hydrauliccylinder, connecting the driven end of said second hydraulic cylinder tosaid inner section, unlocking said inner section from said remainingsections, extending said inner section by extending said secondhydraulic cylinder, unlocking said intermediate section from the fixedsection in response to complete extension of said inner section, andextending said intermediate section by extending said second hydrauliccylinder.

9. In a telescoping boom having an outer fixed section and at leastmovable intermediate and inner boom sections, means for connecting afirst power cylinder between the outer and intermediate boom sectionsfor extending the latter, means for connecting a second power cylinderbetween the intermediate and inner boom sections for extending thelatter, each of the cylinders including telescoping rod and caseelements defining cavities effective to cause extension and retractionof the cylinders in reponse to fluid pressure, fluid supply means fordirecting fluid under pressure successively through the first and secondcylinders, latch means for preventing extension of the intermediate boomsection until the inner boom section has been extended, sequencing valvemeans interconnecting the extension cavities of the cylinders forpreventing fluid flow from the extension cavity of the second cylinderto the extension cavity of the first cylinder in response to fluidpressure in the retraction cavities of the cylinders until said firstcylinder has been substantially completely retracted, said cylinderconnecting means for each cylinder includes diametrically opposed setsof spaced lugs disposed to receive vertical pins between them, and meanson said movable boom sections defining bosses for retaining saidvertical pins and for cooperating with said pins and lugs to transmitextension and retraction forces between said boom sections cylinders andlatch means. 7

10. The boom of claim 9 wherein said spacing between said lugs isdefined by straight vertical surfaces, and said vertical pins have adiameter less than said spacing for permitting relative sliding motionbetween said lugs and said vertical pins upon deflection of the boomunder load.

11. The boom of claim 9 wherein said lugs are located on the rearportion of the cylinder case elements.

12. The boom of claim 9 wherein an auxiliary boom section istelescopingly received within said inner boom section, a set ofapertures in said outer intermediate and inner boom sections inalignment for inserting said vertical pins associated with said secondcylinder when said boom sections are retracted, connector means securedto the outward end of said second cylinder, alignable openings in saidconnector means auxiliary and inner boom sections, a first removable pininsertable through alignable openings in said connector means and saidauxiliary section to drivingly connect said second cylinder to saidaxuiliary boom section, and retaining means for retaining said verticalpins in a partially inserted position to disengage said second cylinderand lock said inner intermediate and outer boom sections together.

13. The boom of claim 12 wherein a second removable pin is insertable inalignable openings to lock said inner and auxiliary boom sectionstogether when said auxiliary section is either in an extended orretracted position.

14. In a telescoping boom having concentric sections including an outerfixed section and extendible intermediate and inner sections that areextended and retracted by a hydraulic cylinder having one end pivotallyconnected to the fixed outer section, wherein the improvement comprisesspaced lug means radially disposed on opposite sides of the other end ofthe cylinder, apertures in the intermediate and outer boom sections thatare in alignment when said intermediate section is retracted, pinreceiving bosses on the intermediate section, vertical pins insertablethrough said apertures and between said lug means to connect the otherend of said cylinder to the intermediate section, and retaining meansfor retaining said vertical pins in a partialiy inserted position insaid apertures out of engagement with said lug means and locking theintermediate and outer boom sections together. k i

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. I3,770,138

DATED November 6, 1973 INVENTOR(S) 2 PAUL A. CHALUPSKY et a1 It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Col. 4, line 63, change "3" to 38--.

Col. 11, line 6, change "exists" to -exits--.

Col. 12, line 50, change "6" to --2--.

Col. 13, line 27, change "telescopigng" to --telescoping--. Col. 14,line 42, change "axuiliary" to --auxiliary--.

Signed and sealed this 29th day of April 1975.

(SEAL) Attest:

C. MARSHALL DANN RUTH C. MASON Comissioner of Patents Attesting Officerand Trademarks

1. In a telescoping boom having an outer fixed section and intermediateand inner sections that are extended and retracted by hydrauliccylinders, each of said hydraulic cylinders being connected at one endto the boom section to be extended and at the other end to the nextradially outermost boom section, each cylinder including two sets ofdiametrically opposed lugs disposed to receive a pin between them, andmeans on said booms defining bosses for retaining pins received betweenthe said lugs, said lugs cooperating with said pins and bosses totransmit the cylinder forces to the boom sections for extension andretraction.
 2. In an extensible boom of the type having a tubular basesection, a tubular mid section slidably received in said base section, atubular inner section slidably received in said mid section, firsthydraulic cylinder means pivotally connected to base section anddisposed in said base and mid sections, second hydraulic cylinder meanspivotally connected at one end to said mid section and disposed in saidmid and inner sections, the improvement which comprises laterally spacedlug means radially disposed on opposite sides of each of said cylinders,means defining alignable openings in said base and in said mid and innerboom sections, first pin means insertable through the apertures in saidmid section when in alignment and between said lug means of said firstcylinder connecting said first cylinder in driving engagement with saidmid section, and second pin means insertable through the apertures insaid inner section and between said lug means of said second cylinder toconnect said second cylinder in driving relation with said innersection.
 3. The apparatus of claim 6 including an auxiliary sectionslidably received in said inner section and disposed in a surroundingrelationship to said second cylinder connector means secured to theoutward end of said cylinder, third removable pin means insertablethrough alignable openings in said connector means and said auxiliarysection; and retaining means for retaining said second pin means in apartially inserted position in the aligned apertures of said base, midand inner sections but out of engagement with said lugs whereby saidbase, mid and inner sections are locked together and said lugs on saidsecond cylinder are disengaged whereby energization of said secondcylinder causes extension of said auxiliary section.
 4. The apparatus ofclaim 2 wherein said lateral spacing between said lugs is defined bystraight vertical surfaces and said pin means vertically receivabletherein have a diameter less than said spacing to permit relativesliding and tilting motion between said lugs and said pin means upondeflection of the boom under load.
 5. The apparatus of claim 2 whereineach cylinder includes a casing and a rod and wherein said lugs arelocated at the rear portion of each casing.
 6. In a telescoping boomhaving concentric sections including an outer fixed section andintermediate and inner sections that are extended and retracted byhydraulic cylinders, each of said hydraulic cylinder being connected atone end by pin means to the boom section to be extended and at the otherend to the next radially outermost boom section, wherein the improvementcomprises an extendible auxiliary boom section within said innersection, pin and aperture means effective to alternately lock said innerand auxiliary sections together when said auxiliary section is either ina fully extended position or in a fully retracted position, said pin andaperture means also being effective to connect the hydraulic cylinderassociated with said inner section to the auxiliary section forextension and retraction thereof, and the pin means associated with saidinner section being movable to a position where the associated hydrauliccylinder is disconnected therefrom and said inner, intermediate andouter sections are locked together.
 7. A method of extending a crAneboom, having at least two extendible telescopigng sections mountedwithin a fixed section by means of a single hydraulic cylinder havingits driving end attached to said fixed section, comprising the steps ofconnecting the driven end of said cylinder to the first section to beextended, connecting the remaining sections to said fixed section,extending said first section by extending said hydraulic cylinder,locking said first section to a second section, disconnecting saiddriven end of said cylinder, retracting said cylinder, connecting thedriven end of said cylinder to said second section, disconnecting saidsecond section from said fixed section, and extending said secondsection by extending said hydraulic cylinder.
 8. A method of extending atelescoping boom having concentric sections including an outer fixedsection, intermediate, inner and auxiliary sections wherein a firsthydraulic cylinder has its driving end connected to said fixed sectionand its driven end to said intermediate section, a second hydrauliccylinder has its driving end connected to said intermediate section andits driven end to said inner section comprising the steps of connectingthe driven end of said second cylinder to the auxiliary section to beextended, disconnecting the driven end of said second cylinder from saidinner section, locking the remaining sections to said fixed section,extending said auxiliary section by extending said second hydrauliccylinder, locking said auxiliary section to the inner section,disconnecting said driven end of said second hydraulic cylinder,retracting said second hydraulic cylinder, connecting the driven end ofsaid second hydraulic cylinder to said inner section, unlocking saidinner section from said remaining sections, extending said inner sectionby extending said second hydraulic cylinder, unlocking said intermediatesection from the fixed section in response to complete extension of saidinner section, and extending said intermediate section by extending saidsecond hydraulic cylinder.
 9. In a telescoping boom having an outerfixed section and at least movable intermediate and inner boom sections,means for connecting a first power cylinder between the outer andintermediate boom sections for extending the latter, means forconnecting a second power cylinder between the intermediate and innerboom sections for extending the latter, each of the cylinders includingtelescoping rod and case elements defining cavities effective to causeextension and retraction of the cylinders in reponse to fluid pressure,fluid supply means for directing fluid under pressure successivelythrough the first and second cylinders, latch means for preventingextension of the intermediate boom section until the inner boom sectionhas been extended, sequencing valve means interconnecting the extensioncavities of the cylinders for preventing fluid flow from the extensioncavity of the second cylinder to the extension cavity of the firstcylinder in response to fluid pressure in the retraction cavities of thecylinders until said first cylinder has been substantially completelyretracted, said cylinder connecting means for each cylinder includesdiametrically opposed sets of spaced lugs disposed to receive verticalpins between them, and means on said movable boom sections definingbosses for retaining said vertical pins and for cooperating with saidpins and lugs to transmit extension and retraction forces between saidboom sections cylinders and latch means.
 10. The boom of claim 9 whereinsaid spacing between said lugs is defined by straight vertical surfaces,and said vertical pins have a diameter less than said spacing forpermitting relative sliding motion between said lugs and said verticalpins upon deflection of the boom under load.
 11. The boom of claim 9wherein said lugs are located on the rear portion of the cylinder caseelements.
 12. The boom of claim 9 wherein an auxiliary boom section istelescopingly received within said inner boom section, a seT ofapertures in said outer intermediate and inner boom sections inalignment for inserting said vertical pins associated with said secondcylinder when said boom sections are retracted, connector means securedto the outward end of said second cylinder, alignable openings in saidconnector means auxiliary and inner boom sections, a first removable pininsertable through alignable openings in said connector means and saidauxiliary section to drivingly connect said second cylinder to saidaxuiliary boom section, and retaining means for retaining said verticalpins in a partially inserted position to disengage said second cylinderand lock said inner intermediate and outer boom sections together. 13.The boom of claim 12 wherein a second removable pin is insertable inalignable openings to lock said inner and auxiliary boom sectionstogether when said auxiliary section is either in an extended orretracted position.
 14. In a telescoping boom having concentric sectionsincluding an outer fixed section and extendible intermediate and innersections that are extended and retracted by a hydraulic cylinder havingone end pivotally connected to the fixed outer section, wherein theimprovement comprises spaced lug means radially disposed on oppositesides of the other end of the cylinder, apertures in the intermediateand outer boom sections that are in alignment when said intermediatesection is retracted, pin receiving bosses on the intermediate section,vertical pins insertable through said apertures and between said lugmeans to connect the other end of said cylinder to the intermediatesection, and retaining means for retaining said vertical pins in apartially inserted position in said apertures out of engagement withsaid lug means and locking the intermediate and outer boom sectionstogether.